Photoelectrochemical glycerol oxidation on Mo-BiVO4 photoanodes shows high photocharging current density and enhanced H2 evolution.

Mo-doped BiVO4's lower efficiency can be attributed in part to exciton recombination losses. Recombination losses during photoelectrochemical water oxidation can be eliminated by using glycerol as a hole acceptor. This results in an enhanced photocurrent density. In this research, we present the synthesis of a Mo-doped BiVO4 photoelectrode with a greater photocurrent density than a traditional pristine photoanode system. Increased photon exposure duration in the presence of glycerol leads to 8 mA cm-2 increase in photocurrent density due to the creation of a capacitance layer and a decrease in charge transfer resistance on the photoelectrode in a neutral-phosphate buffer solution thus confirming the photo charging effect. Glycerol photooxidation improves the photoelectrode's rate of hydrogen evolution. Research into the effects of electrolyte and electrode potential on photoelectrodes has revealed that when the applied potential increases, the light absorbance behaviour changes following its absorption distribution over the applied potential. Under a transmission electron microscope (TEM), a unique dynamical crystal fringe pattern is found in the nanoparticles scratched from the photoelectrode.

Atomic-scale changes of silica-supported catalysts with nanocrystalline or amorphous gallia phases: implications of hydrogen pretreatment on their selectivity for propane dehydrogenation.

This work explores how H2 pretreatment at 550 °C induces structural transformation of two gallia-based propane dehydrogenation (PDH) catalysts, viz. nanocrystalline γ/ß-Ga2O3 and amorphous Ga2O3 (GaO x ) supported on silica (γ-Ga2O3/SiO2 and Ga/SiO2, respectively) and how it affects their activity, propene selectivity and stability with time on stream (TOS). Ga/SiO2-H2 shows poor activity and propene selectivity, no coking and no deactivation with TOS, similar to Ga/SiO2. In contrast, the high initial activity and propene selectivity of γ-Ga2O3/SiO2-H2 decline with TOS but to a lesser extent than in calcined γ-Ga2O3/SiO2. In addition, γ-Ga2O3/SiO2-H2 cokes less than γ-Ga2O3/SiO2. Ga K-edge X-ray absorption spectroscopy suggests an increased disorder of the nanocrystalline γ/ß-Ga2O3 phases in γ-Ga2O3/SiO2-H2 and the emergence of additional tetrahedral Ga sites (GaIV). Such GaIV sites are strong Lewis acid sites (LAS) according to studies using adsorbed pyridine and CO probe molecules, i.e., the abundance of strong LAS is higher in γ-Ga2O3/SiO2-H2 compared to γ-Ga2O3/SiO2 but lower than in Ga/SiO2 and Ga/SiO2-H2. Dissociation of H2 on the Ga-O linkages in γ-Ga2O3/SiO2-H2 yields high-frequency Ga-H bands that are observed in Ga/SiO2 and Ga/SiO2-H2 but not detected in γ-Ga2O3/SiO2. We attribute the increased amount of GaIV sites in γ-Ga2O3/SiO2-H2 mostly to an increased disorder in γ/ß-Ga2O3. X-ray photoelectron spectroscopy detects the formation of Ga+ and Ga0 species in both Ga/SiO2-H2 and γ-Ga2O3/SiO2-H2. Therefore, it is likely that a minor amount of GaIV sites also forms through the interaction of Ga+ (such as Ga2O) and/or Ga0 with silanol groups of SiO2.

Soledad y envejecimiento / Loneliness and ageing

El objetivo del estudio es conocer la prevalencia de soledad y aislamiento social en mayores de 65 años en Ourense y sus factores asociados. Métodos: estudio descriptivo trasversal, muestra aleatoria de personas mayores de 65 años a las que se realizó una entrevista entre junio de 2010 y junio de 2011. Tamaño muestral: 486 pacientes (soledad estimada del 35%). Se administró la escala OARS-MFAQ (Olders American Resource and Services Multidimensional Functional Assessment Questionnaire), que recoge variables sociodemográficas, recursos sociales, económicos, salud física, mental y la capacidad para llevar a cabo actividades básicas de la vida diaria (ABVD) y actividades instrumentales de la vida diaria (AIVD). Se les hizo la pregunta «¿Se encuentra usted sola/solo?», con cuatro posibles respuestas: siempre, a menudo, casi nunca, nunca. Resultados: se entrevistó a 572 personas de una edad media de 79 años (desviación estándar [DE]: 6,79). Soledad: 32,7%; vive sola/solo: 17%; sin contacto semanal: 18,9%; aislamiento social: 1,4%. Fueron factores asociados a la percepción de soledad: ser mujer, tener pensión y nivel educativo bajos, depresión, deterioro cognitivo, pérdida de visión, dependencia para las AVBD, tomar psicofármacos en los 6 meses previos y la necesidad de mejoras en la vivienda. La práctica de ejercicio regular constituyó un factor protector. Conclusiones: la soledad en nuestra población es similar a la descrita en otros ámbitos, se asocia a desigualdad de género, factores sociales y demográficos, depresión y deterioro cognitivo. Los profesionales de Atención Primaria deben identificarla y abordarla.(AU)

The aim of this research is to ascertain the prevalence of loneliness and social isolation in people aged over 65 in Ourense and its associated factors. Methods: descriptive cross-sectional study, random sample of people aged over 65 interviewed between June 2010 and June 2011. Sample size was 486 patients (estimated loneliness 35%). The OARS (Olders American Resource and Services Multidimensional Functional Assessment Questionnaire) scale was administrated. This includes sociodemo-graphic variables, socio-economic resources, physical and mental health and the ability to undergo BADL and IADL. The question “are you alone?” with four possible answers was also posed. Results: a total of 572 people were interviewed, aged on average 79 years old (SD: 6.79). Loneliness 32.7%; living alone 17.0%; no weekly contacts 18.9%; social isolation (living alone + no contacts) 1.4%. Feelings of loneliness were associated with sex (women), low pension and educational level, depression, cognitive impairment, vision loss, dependence for BADL, psychopharmacological treatment in the previous six months and the need for home improvements. Regular physical exercise was a protective factor. Conclusions: loneliness in our population is similar to the one reported in other areas. It is associated with sex inequalities, social and demographic factors, depression and cognitive impairment. Primary care professionals need to identify and tackle loneliness.(AU)

Peering into buried interfaces with X-rays and electrons to unveil MgCO3 formation during CO2 capture in molten salt-promoted MgO.

The addition of molten alkali metal salts drastically accelerates the kinetics of CO2 capture by MgO through the formation of MgCO3 However, the growth mechanism, the nature of MgCO3 formation, and the exact role of the molten alkali metal salts on the CO2 capture process remain elusive, holding back the development of more-effective MgO-based CO2 sorbents. Here, we unveil the growth mechanism of MgCO3 under practically relevant conditions using a well-defined, yet representative, model system that is a MgO(100) single crystal coated with NaNO3 The model system is interrogated by in situ X-ray reflectometry coupled with grazing incidence X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy. When bare MgO(100) is exposed to a flow of CO2, a noncrystalline surface carbonate layer of ca. 7-Å thickness forms. In contrast, when MgO(100) is coated with NaNO3, MgCO3 crystals nucleate and grow. These crystals have a preferential orientation with respect to the MgO(100) substrate, and form at the interface between MgO(100) and the molten NaNO3 MgCO3 grows epitaxially with respect to MgO(100), and the lattice mismatch between MgCO3 and MgO is relaxed through lattice misfit dislocations. Pyramid-shaped pits on the surface of MgO, in proximity to and below the MgCO3 crystals, point to the etching of surface MgO, providing dissolved [Mg2+…O2-] ionic pairs for MgCO3 growth. Our studies highlight the importance of combining X-rays and electron microscopy techniques to provide atomic to micrometer scale insight into the changes occurring at complex interfaces under reactive conditions.

Uncovering selective and active Ga surface sites in gallia-alumina mixed-oxide propane dehydrogenation catalysts by dynamic nuclear polarization surface enhanced NMR spectroscopy.

Gallia-alumina (Ga,Al)2O3(x : y) spinel-type solid solution nanoparticle catalysts for propane dehydrogenation (PDH) were prepared with four nominal Ga : Al atomic ratios (1 : 6, 1 : 3, 3 : 1, 1 : 0) using a colloidal synthesis approach. The structure, coordination environment and distribution of Ga and Al sites in these materials were investigated by X-ray diffraction, X-ray absorption spectroscopy (Ga K-edge) as well as 27Al and 71Ga solid state nuclear magnetic resonance. The surface acidity (Lewis or Brønsted) was probed using infrared spectroscopy with pyridine and 2,6-dimethylpyridine probe molecules, complemented by element-specific insights (Ga or Al) from dynamic nuclear polarization surface enhanced cross-polarization magic angle spinning 15N{27Al} and 15N{71Ga} J coupling mediated heteronuclear multiple quantum correlation NMR experiments using 15N-labelled pyridine as a probe molecule. The latter approach provides unique insights into the nature and relative strength of the surface acid sites as it allows to distinguish contributions from Al and Ga sites to the overall surface acidity of mixed (Ga,Al)2O3 oxides. Notably, we demonstrate that (Ga,Al)2O3 catalysts with a high Al content show a greater relative abundance of four-coordinated Ga sites and a greater relative fraction of weak/medium Ga-based surface Lewis acid sites, which correlates with superior propene selectivity, Ga-based activity, and stability in PDH (due to lower coking). In contrast, (Ga,Al)2O3 catalysts with a lower Al content feature a higher fraction of six-coordinated Ga sites, as well as more abundant Ga-based strong surface Lewis acid sites, which deactivate through coking. Overall, the results show that the relative abundance and strength of Ga-based surface Lewis acid sites can be tuned by optimizing the bulk Ga : Al atomic ratio, thus providing an effective measure for a rational control of the catalyst performance.